Not so rare: visual changes in people with more common forms of dementia

This week we’ve heard about visual symptoms in people who have dementia, and in people with posterior cortical atrophy it’s particularly clear that these are prominent symptoms. In this article we’ll discuss whether people with other forms of dementia may also experience visual changes - perhaps as a less prominent symptom or at a later stage of disease when it might not be so easy to see them as separate from other symptoms, and to describe the effect that they have.

When we compare the areas of the brain that are affected in posterior cortical atrophy to the areas affected in more typical memory-led Alzheimer’s disease, we find that people with PCA have more atrophy (shrinkage) at the back of the brain - the parietal and occipital lobes, whilst people with typical Alzheimer’s disease have more atrophy in an area called the medial temporal lobe, which is important for aspects of memory. However, typical Alzheimer’s disease can also affect those areas at the back of the brain. From studies that have looked in detail at how Alzheimer’s disease spreads and affects more and more areas of the brain over time, we know that at later stages of the disease, the parietal (and eventually also occipital lobes) may become affected even in typical Alzheimer’s disease. This leads us to think that people at later stages of typical Alzheimer’s disease may also experience visual symptoms similar to the visual symptoms experienced in earlier stages of posterior cortical atrophy. Understanding that this is a possibility may be helpful in order to understand and care for people at later stages, for example they may benefit from some of the environmental adaptations that people with PCA find useful such as ensuring there is good lighting and good colour contrast for objects that need to be perceived clearly.

A number of researchers have studied visual symptoms in typical Alzheimer’s disease and found some signs of changes. To give one example, a study by Rizzo and colleagues [1] found that people with typical Alzheimer’s disease perform worse than healthy participants on tests measuring sensitivity to contrast, drawing and visual aspects of attention. There is some evidence that simple interventions that try to get around these problems may be helpful, for example one study found that increasing contrast in tableware (using high-contrast red or blue instead of white tableware) helped with eating and drinking [2]. The existence of these kinds of visual problems also fits with stories that people who work in care homes sometimes share such as people with Alzheimer’s disease misinterpreting a black floor mat as a hole, which may cause anxiety or hesitancy when walking around.

As we heard in last week, dementia with Lewy bodies is also associated with visual changes, particularly hallucinations, and also more basic aspects of visual perception. These changes may be more prominent than those seen in typical Alzheimer’s disease. In one study, people who had dementia with Lewy bodies had more difficulty with tasks such as judging size of objects, counting objects visually and identifying figures that overlap with each other [3].

It’s important to remember to check that ‘eye sight’ is good, even when ‘brain sight’ is impaired, and having the correct glasses, and checking for problems with the eyes is essential to ensuring that people maintain their visual function as best as possible. Even if the brain has difficulty interpreting information from the eyes, we should try to ensure it gets the best signal from the eyes, and if people with dementia don’t have the right prescription or have other eye problems that haven’t been attended to they won’t have the best vision that they can.